In most large lightweight concrete elements, use is made of a reinforcement in the form of a bent welded mesh or so-called cage. Such cages are manufactured in that a number of longitudinal reinforcement steel wires are welded to transversal wires or pins in a welding machine for this particular purpose, while forming a planar mesh which is then bent so as to fit in the lightweight concrete element. Each cage is adapted to or fixed in the mould prior to or in direct connection with the casting of the fresh concrete which forms the lightweight concrete. The cage is suspended in the mould by means of a holding means comprising a number of vertical needles which are connected with a corresponding number of metal plates provided with holes and serving as attachment members, said plates being arranged on some of the cross pins included in the mesh or cage depending on the length of the lightweight concrete element, the number of attachment plates varies, and they may occur on, e.g., every five to ten cross pins of the mesh.
Conventional type welding machines usually comprise magazines which allow the cross pins to fall or roll down to the longitudinal rods, the cross pins being retained in the desired positions by means of magnets or the like until secured by the welding tongs. Such machines involve considerable difficulties in supplying plate-carrying cross pins, since the plates must be oriented in a certain direction and cannot be allowed to swing. From considerations of space, it has, in actual practice, further been impossible to install twin magazines for different types of cross pins, i.e. naked pins and plate-carrying pins. As a rule, this problem has been solved in that the plate-carrying cross pins are welded manually in a separate operation. An alternative solution is to fix the pins in a welding fixture which is then advanced through the welding machine, but in this case, the freedom of choosing the number of pins is restricted.